1. Field of the Invention
The present invention relates to a workpiece conveying apparatus (workpiece conveying robot) for a pressing machine (press machine).
2. Description of the Related Art
Hitherto, there have been proposed various workpiece conveying apparatus configured to carry workpieces into and out of a press machine, or carry workpieces between the press machines.
For example, in Patent Literature 1, there is described a workpiece conveying apparatus as illustrated in FIG. 13A. The workpiece conveying apparatus can mutually independently control arm units of two selective compliance assembly robot arm robots (SCARA robots), and distal ends of the arm units of the SCARA robots are coupled to each other by slide arms.
Herein, Patent Literature 1 corresponds to Japanese Patent No. 5274053.
Here, the related-art workpiece conveying apparatus cannot perform a feeding axis rotation (rolling), that is, an operation of rotating a workpiece about an axis extending along a workpiece conveying direction. Accordingly, in actuality, there is difficulty in adopting the related-art workpiece conveying apparatus, for example, when it is desired that a workpiece W in an oblique state be fed to a die for a subsequent step, which is often desired by European manufacturers and the like.
In this context, in the workpiece conveying apparatus described in Patent Literature 1, lifting shafts (shafts extending in a height direction) arranged on right and left raising and lowering mechanisms are shifted to different phases to incline a support frame (entire apparatus). In this way, the feeding axis rotation (rolling) is enabled.
However, this method involves a problem in that higher rotational energy is required, and a motor size needs to be increased, with the result that the apparatus is increased in size. Further, as illustrated in FIG. 13B, the entire arm units are inclined to enter a press. Accordingly, in actuality, there is a high risk of interference between inclined arms and an upper die, with the result that it is necessary to increase a stroke of the press. Further, in the workpiece conveying apparatus described in Patent Literature 1, it is necessary to incline the arm units elongated laterally within a plane of the drawing sheet of FIG. 13B. In other words, when an inclination angle is equal, amplitude of vibration increases as the arm units become longer. Accordingly, the arm units are liable to interfere with other components. Thus, in actuality, a large inclination angle cannot be taken.